川东南龙马溪组页岩的矿物组成与微观储集特征研究

通过岩石学特征、矿物组成、微观孔隙和力学性质等分析,对川东南地区龙马溪组页岩的矿物组成与微观储集特征进行了综合研究。研究结果表明,龙马溪组页岩主要由石英和黏土矿物组成,平均含量分别为36.07%和41.55%,碳酸盐岩含量较低,平均9.92%,底部石英含量最高,向上含量降低,黏土含量增加;页岩中硅质含有丰富的生物碎屑,表明主要为生物成因。页岩主要发育有机质孔隙和无机矿物孔隙,后者的粒缘微裂缝较发育,而粒内和粒间孔隙相对较少。页岩中石英含量与页岩孔容呈正相关关系,表明生物来源硅质的孔隙对页岩总孔隙有重要贡献,生物来源硅质的存在也提高了页岩脆性,有利于储层的后期压裂改造。

Mineral composition andmicroscopic reservoir features of Longmaxi shales in southeastern Sichuan Basin

Mineral compositions and microscopic reservoir features of the Longmaxi shales in the southeastern Sichuan Basin were comprehensively studied using the analyses of petrological characteristics, mineral compositions, microscopic pore structures and rock mechanics.The results show that quartz and clay minerals are abundant in the Longmaxi shales with average contents of 36.07% and 41.55% respectively, while carbonate minerals are poor with an average content of 9.92%.Quartz is especially rich at the bottom of the Longmaxi shales. As burial depth decreases, the content of quartz is less while clay mineral content increases. Abundant bioclasts indicate that siliceous matter is mainly biogenetic. Many inorganic and organic pores are found in the Longmaxi shales. Granular margin micro-fractures develop well in inorganic pores,while intergranular and intragranular pores are less common. There is a positive correlation between quartz content and pore volume, which indicates that biogenic silica pores play an important role in the development of porosity.Biogenic silica contributes to a high content of brittle minerals, which is favorable for fracturing treatment.